Mechanism for regulating fuel injection in free piston engines



March 1954 H. G. SPIER ETAL MECHANISM FOR REGULATING FUEL INJECTION INFREE PISTON ENGINES 2 Sheets-Sheet 1 Filed May 12. 1950 MM-LE urn-2 31mINVENTOR. Hans G. Jp/er BY Aober/ las/e'y ATTORNEYS March 1954 H. G.SPIER ETAL MECHANISM FOR REGULATING FUEL INJECTIQN IN FREE PISTONENGINES 2 Sheets-Sheet 2 Filed May 12. 1950 a V010 A u 6 f mm WHLI HR I9 Wm. W

Patented Mar. 9, 1954 MECHANISM FOR REGULATING FUEL INJECTION IN FREEPISTON ENGINES Hans George Spier and Robert Lasley, Hamilton,

Ohio, assignors, by mesne assignments, to Baldwin-Lima-HamiltonCorporation, a corporation of Pennsylvania Application May 12, 1950,Serial No. 161,566

7 Claims. 1

This invention relates to a fuel injection and starting system for freepiston engines, and is particularly directed to the improvementcomprising a control mechanism for regulating the injection of fuel.

In starting engines of the free piston type, it is customary to employ arelatively large fuel charge. While this large charge is desirable inthe initial combustion cycle, continued feeding of similar large fuelcharges is undesirable and unsatisfactory. Manual control means may beemployed for cutting back the fuel injection, but this is notsufficiently rapid or positive in its operation. Furthermore, the fuelcut back is preferably followed by a gradual increase in fuel as theengine picks up its load in normal operation.

Various systems of fuel injection have been proposed for free pistonengines which differ from those used in conventional compressionignition engines, since the matter of timing the injection as well asvarying its quantity are both of utmost importance for successfuloperation. In conventional engines, a shaft having a complete rotarymovement can be timed in relation to the engine crankshaft and used tooperate the fuel pumps. In free piston engines such a shaft is notordinarily available, and further it will be seen that injection takesplace at a'point in the cycle when the pistons have nearly stopped ontheir inward strokes. The relatively slow movement of the reciprocatingparts makes precise fuel injection timing diflicult with equipmentpatterned after the familiar diesel injection systems. The presentinvention includes means to determine a change in quantity of fuelinjection in accordance with an overstroke of the engine. For eachquantity of injected fuel it has been found that there exists an optimumtime of injection, so that the invention comprises also a means toreestablish the time of injection as each new setting of fuel quantityis made.

It is, therefore, the primary object of the present invention to providea fuel injection system for a free piston engine in which the time ofinjection is varied as the quantity of injected fuel is varied; in whichthe quantity of injected fuel is either manually or automaticallyestablished but capable of automatic variation to compensate foroverstroking of the free pistons; in which the quantity of injected fuelis deliberately made abnormally large during starting but cut back to alesser quantity-automatically when the engine is running; and in whichmeans are provided to maintain a constant volumetric ratio of fuelpassing through two or more injection nozzles.

Other objects and advantages of the present invention will becomeapparent from the following detailed description thereof when read inconjunction with the accompanying drawings, in which:

Fig. 1 is a diagrammatic side elevation, partly in section, of a freepiston engine, and

Fig. 2 is a diagrammatic sectional view of a fuel injection controlmechanism representing one embodiment of the present invention.

In the free piston engine shown in Fig. 1, each of the free pistons isdivided into three parts: a combustion piston ID, a compressor piston lland a bounce piston I2. The power cylinder I3 is provided with upper andlower fuel injectors i4 and a scavenging air inlet l5, in addition tothe usual exhaust ports IS.

The compressor pistons i I reciprocate within a compressor cylinder I1,and air from the cylinder I! may be fed as scavenging air to the powercylinder l3 in the usual manner. The bounce pistons l2 move back andforth in bounce cylinders i8 and the air compressed within the bouncecylinders, in addition to being used as a cushion to restore the pistonsto the center of the power cylinder on a compression stroke may be usedin controlling the extent and frequency of the strokes of the freepistons. The volume 59' in front of the compressor pistons ll oppositethe compressor cylinder volumes, is used as a reverse bounce cylinder,since the gases within the volume i9 may be used to assist incontrolling the movement of the free pistons in the reverse direction.Synchronizing racks 20 are attached to each of the compressor pistons Hand extend out through the reverse bounce chambers I9 to engage a pinion2 l, in this manner assuring synchronous movement of the free pistons.Power from the system is customarily derived as energy contained in theexhaust gases and is converted to work in a turbine or similar consumer.

In starting free piston engines, as disclosed in the co-pendingapplication of Lewis and Morain, Serial No. 633,222, filed December '6,1945, now Patent 2,600,251, issued June 10, 1952, the first step is tointroduce air under pressure into the reverse bounce chambers i9, thusforcing the compressor pistons H outwardly into the outermost position.The starting mechanism for the free piston enginedisclosed in Fig. 1 isdiagrammatically shown, element 22 representing a source of compressedair from which a line 24 leads to volume It. Valves 25 control theintroductionof air into the reverse bounce chambers t9. When the pistonsII have moved outwardly, air pressure is built up within the directbounce cylinders I3. Dump valves 26 regulate the flow of gas from thereverse bounce chambers l9 and are operated by air pressure from line 28when valve 29 is open. The tripping of the dump valves 26 upon theopening of the valve 29 relieves the pressure in the reverse bouncechamber and permits the pressure within the direct bounce cylinders Hito force the free pistons inwardly toward the innermost or combedposition. A ballistic timer 30 is so regulated that the air pressure inthe line 28 leading to the dump valves 26 drops to about zero (oratmospheric pressure) at the time the free pistons reach a predeterminedpoint in their inward stroke, thus closing the dump valves 26. From thispoint on, the engine operates with the dump valves closed and air valves25 and 29 are also closed.

The present invention comprises a novel fuel injection mechanism shownin detail in Fig. 2 and includes a housing 3| having formed therein aninjection pump cylinder 32. A pump plunger 34 reciprocates within thecylinder 32 and has a reduced section 35 on which a spiral shaped landsegment 36 is formed to control the quantity and time of injection ashereafter described. Reciprocation of the pump plunger 34 is effected bythe rotation of a segment gear 38 meshing with synchronizing pinion 2|which aotuates in turn an eccentric 39. A connecting rod 40 mounted uponthe eccentric 39 is connected to the pump plunger 34 through ball andsocket engagement with a crosshead or plunger 4!. As a result, themovement of the pump plunger 34 is controlled by the movement of thefree pistons.

Fuel is supplied from a source 42 and passed through a filter 44 into agear pump 45, which combines with bypass valve 46 to maintain thedesired pressure within the fuel lines. A second filter 48 filters thepressurized fuel which then passes into fuel line 49 and through line 55and port into cylinder 32 and pump cavity 52. A spill port 54 isconnected by line 55 to a drain 56 through a check valve 58.

Fuel line 49 is connected to an accumulator pump 59 through a one-wayvalve 50. The accumulator pump acts to maintain a body of liquid(conveniently fuel oil) under a very high pressure. A small compressorpiston 6| is connected at one end to a drive piston 52 mounted in adrive cylinder 64. By maintaining air pressure in the cylinder 64 fromany convenient air source by means of a pressure regulator 55, thecompressor piston 6| is made to force fuel oil under high pressurethrough a one-way valve 66 and feed line 68 into an accumulator volume69. The ratio of pressure increase from air line to accumulator volumeis determined by the relative areas of pistons 62 and 6 As pump plunger34 moves inwardly in cylinder 32 fuel is forced from cavity 52 throughcheck valves '10 into separate feed chambers 7|, Ha. This introductionof fuel into the feed chambers 1|, Ha, forces distributor pistons 72 and14 in the direction of the accumulator and against the high pressuremaintained therein by the accumulator pump 59. The triggering needles T3are held to their seats by the pressure of the fuel being pumped sincethe area of the rear ends, exposed in chamber 52, is greater than thearea of the front ends exposed in chambers 1|, 1| a. When spill port 54is opened by reason of the land 36 overrunning it, the pressure withincylinder 32 and pump cavity 52 is relieved. The pressure at the rear ofthe resiliently mounted triggering needles 18 is thus reduced and theneedles are moved rearwardly against the mounting springs 19 by thepressure of the fuel on the front ends within the feed chambers H, Hathus permitting fuel to flow through lines to nozzles 8|. Sincedistributor pistons 12 and I4 are mechanically interconnected, thequantity of fuel delivered to the nozzles 8| will vary in directproportion to the bottom area of the respective distributing pistons. Itwill be seen that the pressure of injection is determined by thepressure in the accumulator volume 69 and not directly by the injectionpump. Further, the time of injection is determined by the time ofopening spill port 54 to relieve the pressure in the pump chamber 52,which time is determined by the shape of the outer side of segment orland 36. A constant injection time could be obtained if this land wereto be formed as a circle normal to the axis of the pump plunger 34. Ithas been found, however, that for each quantity of fuel, or for eachengine load, there exists a different optimum time of injection. Theouter surface of land 36 is thus ground to maintain this optimum timingwith each setting of the pump plunger 34.

In prior devices of this character, in which fuel is forced through thenozzles by accumulated pressure, the time of cutoff is determined solelyby the time when the nozzle springs or the springs tending to seat thevalves 18 overcome the accu mulator pressure. As these forces approacheach other in magnitude there is a tendency for the valves to bounce sothat the last of the injection is made irregularly and in an uncertainmanner. By the present invention piston 14 is provided with an enlargedhead 15 which cooperates with a seat 16 in the accumulator body to limitthe extent of movement of piston 14 in the direction which causedinjection. Since the pressure of the accumulator drops only slightlyduring injection, the time of cut-off is determined entirely by the timewhen head 15 strikes seat 16 and not by any drop in pressure in theaccumulator, and all of the fuel is injected under high pressure.

The plunger 34 may be varied in position by turning it in the cylinderin a manner well known in the art. The plunger is thus diagrammaticallyshown as carrying a gear 84 adapted to mesh with a positioning rack 86.As the rack is moved to rotate gear 84 the position of the land 36 willbe changed so that both the quantity of fuel and the time of injectionwill be varied. The present invention provides a manual and overridingautomatic means to move the fuel rack.

The fuel rack is connected to an operating rod 85 which can be manuallymoved by a handle 88 pivoted at 89. A spring link 90 is provided betweenthese elements, however, so that the rod 86 and its associated rack canbe moved independently of the manually set handle. A T- shaped lever 9|is also connected at one of its ends to rod 86 between spring link 90and the injection pump.

Automatic resetting of the fuel rack is accomplished in the presentinvention for two purposes. In the first place, overstroking of the freepistons may be taken as an indication that more fuel is being injectedthan is required to carry the load to which the machine is subjected atthat time. For this reason, a device is provided to cut back the fuel inthe event of overstroking, the device being responsive to pistonposition. Secondly, the fuel rack is adapted by the present invention tobe moved quickly, upon starting, from a position in which a relativelygreat quantity of fuel is injected to a position in which the fuel isgreatly cut back. While these devices are inter-related in that theycontribute to adjustment of the fuel rack position, they will bedescribed in turn.

The overstroke control valve comprises a casing 92 in which is formed acylinder 94. A plunger 95 is resiliently positioned by means of a spring96 within the cylinder 94 and has a passage 98 formed therein. An inletport 99 connects the cylinder 94 with fuel line 49 and port I connectscylinder 94 to the drain 56. Plunger 95 is reciprocated within thecylinder 94 by a bell crank lever IOI which in turn is actuated by camI02, integral in this particular embodiment with segment ear 38.

Cam I02 has its contour cut with slightly increasing height as thepistons recede from each other up to the point where the normal outwardstroke of the pistons is exceeded at which point the contour of the camincreases sharply. Thus in normal stroking of the engine pistons themotion of plunger 95 is a reduced and reversed reproduction of themotion of one of the engine pistons so that as the engine pistons movefarther into the bounce cylinders plunger 95 moves farther to itscylinder 94. The plunger 95, bell crank IOI and cam I02 are soassociated that, during normal stroke operation of the free pistonengine, plunger 95 intermittently connects only the inlet port 99 andoutlet port I04 but during an abnormally long outward stroke oroverstroke of the free pistons, plunger 95 moves inwardly into cylinder94 sufliciently to connect outlet port I04 with drain port I00 torapidly withdraw fluid from cylinder I05.

A control cylinder I05 is connected by a line I08 to the outlet port I04of the overstroke control valve so that fluid (conveniently fuel oil) issupplied through line I08 to the cylinder I05 on one side of a pistonI06. A spring I09 engages the opposite side of the piston I06. A pistonrod H0 is connected to the piston I06 and engages an end I II of theT-shaped lever 9I whenever the engine is overstroking, but is otherwiseheld out of contact with the T-shaped lever 9 I.

Under normal operating conditions, the piston I96 stands in theinnermost position in control cylinder I05 against a stop in thecylinder and spring I09 is compressed. The spring is held in thisposition by reason of the fact that inlet port 99 and outlet port I04are connected to charge the control cylinder at each reciprocation ofthe pistons and in the absence of an overstroke which wouldsimultaneously connect outlet port I 04 with drain port I09 fluid willbe supplied to control cylinder I05 but will not be drained from it.When oil is drained from cylinder I05 by reason of an engine overstrokewhich simultaneously connects ports I04 and I00, spring I09 immediatelyforces piston I06 outwardly of its cylinder against arm III and thusforces the lever 9| to pivot and move .fuel rack 85 in the direction ofcut-off so that. the subsequent stroke of the pistons is made with lessfuel injected.

The body in which cylinder I 05 is formed is also provided with themechanism which controls the fuel quantity upon starting of the unit.Thus, a second cylinder H2 is located adjacent cylinder I95 and has apiston II4 reciprocably mounted therein. A projection H5 is formed onthe piston H4 and extends into cylinder I05 so as to displace apredetermined quantity of fuel.

A third cylinder I I6 has a reciprocably mounted piston II8 positionedtherein and limited in its downward movement by an adjustable seat II9.A piston rod I20 is connected to the piston H8 and engages an arm I2I ofTsshaped lever 9| opposite to the fulcrum from arm II I. Cylinders I I2and I I8 are connected to the dump valve air feed supply 28 through acommon passage way I22.

The mechanism associated with cylinders III!v and H6 acts primarily uponstarting of the free piston engine. Preparatory to starting the engine,the manual control lever 88 is set in the desired position, air isintroduced into the reverse bounce spaces and the pistons are moved backto the farthest position. The high point I03 of the cam I02 thus is inengagement with the bell crank IOI, forcing the plunger 95 into thecylinder 94 until outlet port I04 and spill port I09 are interconnected.As a result. fluid fills cylinder I05 on one side of the piston I06, butis under .no pressure. As previously noted, the engine pistons arepermitted to move in on their initial strokes by pneumatically openingdump valves 26 through line 26. The air pres sure from the dump valveair feed line 28 forces the projection II5 carried by the piston II4into cylinder I05 and into seating engagement with one wall thereof.This same air pressure forces the piston H9 downwardly so that pistonrod I20 engages arm I2I of the T-shaped lever 9] with sufiicient forceto counter-balance the :pressure of the spring I09 against the pistonI06. As the free pistons move inwardly toward each other, the cam I02rotates toward its high point I01, thus withdrawing plunger 95 fromcylinder 94 until inlet port 99 is connected to outlet port I04 andfilling cylinder I05 with fluid under pressure. At the same time theinjection :pump plunger 34 moves upwardly, and fuel is injected throughnozzles 8I.

At about this point in the cycle the ballistic timer opens the dumpvalve air feed line to the atmosphere, so that the air pressure abovepistons H4 and H8 is reduced to almost atmospheric pressure. Hence, thepressure of fluid within the cylinder I05 forces the projection II5 backinto the cylinder II2, which in turn reduces the pressure withincylinder I05. Simultaneously, the force exerted by the piston rod I29against the arm I2I of the reshaped lever .9I is removed so that theforce exerted by spring I09 is now opposed only by the reduced pressureof the fuel within the cylinder I05. Consequently, piston I06 forces thepiston rod IIO against the arm III causing the T-shaped lever 9| torotate about its pivot point I24 and move the arm 86 and rack 85,causing rotation of the pinion 84 in the direction of reducing thequantity of fuel that will be injected on the next stroke.

After the original cut .back of the fuel injection, oil pressure isgradually returned to normal within cylinder I05 due to intermittentconnections between inlet port 99 and outlet port I04 through thecylinder 94. Since the pressure of the fuel and pressure of spring I09on piston I06 balance one another, the pressure exerted by the springlink '90 against the end of the T link -9I gradually restores the fuelinjectionto that position previously established manually by the manualcontrol lever 88.

If it is found desirable to make the cut back of injected fuel quantitygradual, a needle valve I25 may be positioned in cylinder II6 adjacentthe inlet passage I22, to limit the rate at which piston H8 andassociated piston rod I20 can follow the reduction in pressure in thedump 7'- valve air line 28. can be carried to any desired extent.

It is apparent from the above detailed description that the presentinvention provides control mechanism for regulating both the timing andquantity of fuel injection into a free piston engine, and furthermore,that this mechanism requires relatively few elements other than thosenormally associated with engines of this type. Also, the controlmechanism comprising the present invention includes but a singlepressure sensitive element which is used to provide both the automaticcut back when starting the free piston engine as well as for reducingthe fuel injection upon overstroking of the free pistons.

Numerous variations and modifications may be made in the particularembodiment of the invention set forth in the accompanying drawings anddescribed in detail above. For example, fluid pressure from some sourceother than the fuel feed lines may be employed to operate piston I andis associated elements. Also, other sources of air or other types offluid pressure may be employed in place of the air feed from the dumpvalve supply. These particular sources of fluid pressure are, however,the most convenient and advantageously employed. Other variations willbecome apparent to those skilled in the art.

What we claim is:

1. In a fuel injection system for a free piston engine which includes afuel injection pump, means for regulating the quantity of fuel injectedby said pump, and operating means driven by a piston of the engine foractuating the fuel injection pump, the improvement which includes acontrol cylinder, a piston adapted to reciprocate within the controlcylinder, means to supply fluid under pressure to the cylinder on oneside of said piston, means for exerting pressure against the other sideof said piston, a second cylinder, a piston mounted in said secondcylinder and adapted to reciprocate therein, a projection connected toone side of the second piston and extending into the first cylinder todisplace a portion of the fluid therein, means for supplying fluid underpressure to the other side of said second piston, means associated withthe starting mechanism for the free piston engine for regulating thepressure of the fluid supplied to the second cylinder so that fullpressure is applied at the initiation of the first stroke of the freepiston of the engine and drops to approximately zero near thetermination of the first stroke, said drop in pressure causing theprojection on said second piston to withdraw from said control cylinderand thus reduce the fluid pressure therein, and a piston rod connectedto the first piston and engaging the fuel regulating means whereby adrop in pressure of the fluid in the control cylinder effects areduction in the quantity offuel injected into the engine on subsequentstrokes.

2. In a fuel system for a free piston engine which includes a fuelinjection pump, means op erably connected to at least one of the freepistons of the engine for actuating the pump, means for varyingsimultaneously the quantity and time of fuel injection effected by saidpump, a con- This damping of the action trol mechanism including a'member adapted to engage and operate the fuel varying means, fluidpressure means for operating said member so that a reduction in thepressure of the fluid produces a reduction in the quantity of fuelinjected, means responsive to the starting mechanism of the engine toreduce said fluid pressure, and independent means responsive to anoverstroke of the free piston to reduce the fluid pressure.

3. In a fuel injection system for a free piston engine, a fuel pumpcylinder having intake, outlet and spill ports, a piston in saidcylinder having a helical land thereon of suflicient extent to coversaid intake and spill ports simultaneously and during such interval toforce fuel through said outlet ports, separated pressure chambersreceiving fuel from said outlet ports, an accumulator, means underaccumulator pressure for resisting the entry of fuel into said pressurechambers and for maintaining fuel in said chambers under injectionpressure, a plurality of fuel nozzles corresponding in number to andadapted to be brought into communication with said pressure chambers,and trigger valves associated with each pressure chamber and normallyclosing communication between the pressure chamber and associatednozzle, said trigger valves each having a portion exposed to thepressure in said fuel pump cylinder and a portion of smaller areaexposed to the pressure in the pressure chamber with which it isassociated, whereby said trigger valves are opened by pressure in saidpressure chambers when the pressure in said pump cylinder is reduced, byopening of said spill port.

4. In a fuel injection system in accordance with claim 3, separatedpressure chambers of different volume.

5. In a fuel injection system in accordance with claim 4 in which saidhelical land is rotatable and has its outermost surface formed spirallywhereby the time of uncovering said spill ports is changed as said landis rotated.

6. In a fuel injection system is accordance with claim 3 in which saidhelical land is rotatable and has its outermost surface formed spirallywhereby the time of uncovering said spill ports is changed as said landis rotated.

7. In a fuel injection system in accordance with claim 3 and positivemeans to determine the end of the injection period, said means beingconstantly exposed to accumulator pressure on one side.

HANS GEORGE SPIER. ROBERT LASLEY.

References, Cited in the file of this patent UNITED STATES PATENTSNumber Name Date 1,850,250 Von Salis Mar. 22, 1932 1,919,601 Simmen July25, 1933 2,200,892 Pescara May 14, 1940 2,405,043 Meitzler July 30, 19462,461,224 Meitzler Feb. 8, 1949 2,469,739 Meitzler May 10, 19492,497,091 Morain et a1 Feb. 14, 1950 2,502,127 Chittenden et al. Mar.28, 1950

